/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.lsm.wal;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.ClosedChannelException;
import java.nio.channels.FileChannel;

/**
 * write records to wal file
 */
public class WALWriter implements IWALWriter {
    private static final Logger logger = LoggerFactory.getLogger(WALWriter.class);
    // wal file
    private File logFile;
    private FileOutputStream fileOutputStream;
    private FileChannel channel;
    // 4-bit buffer
    private final ByteBuffer lengthBuffer;
    // save wal record serialized byte data
    private final ByteBuffer walBuffer;
    private final boolean forceEachWrite;

    public WALWriter(File logFile, int walBufferSize, boolean forceEachWrite)
            throws FileNotFoundException {
        this.logFile = logFile;
        this.forceEachWrite = forceEachWrite;
        fileOutputStream = new FileOutputStream(logFile, true);
        channel = fileOutputStream.getChannel();
        lengthBuffer = ByteBuffer.allocate(4);
        walBuffer = ByteBuffer.allocate(walBufferSize);
    }

    /**
     * write walRecord to wal file
     *
     * @param walRecord record to be written
     * @throws IOException
     */
    @Override
    public void write(IWALRecord walRecord) throws IOException {
        if (channel == null) {
            fileOutputStream = new FileOutputStream(logFile, true);
            channel = fileOutputStream.getChannel();
        }
        walBuffer.clear();
        walRecord.serialize(walBuffer);
        walBuffer.flip();
        int logSize = walBuffer.limit();
        lengthBuffer.clear();
        lengthBuffer.putInt(logSize);
        lengthBuffer.flip();

        try {
            channel.write(lengthBuffer);
            channel.write(walBuffer);

            if (this.forceEachWrite) {
                channel.force(true);
            }
        } catch (ClosedChannelException ignored) {
            logger.warn("someone interrupt current thread, so no need to do write for io safety");
        }
    }

    @Override
    public void force() throws IOException {
        if (channel != null && channel.isOpen()) {
            channel.force(true);
        }
    }

    @Override
    public void close() throws IOException {
        if (channel != null) {
            if (channel.isOpen()) {
                channel.force(true);
            }
            fileOutputStream.close();
            fileOutputStream = null;
            channel.close();
            channel = null;
        }
    }

    @Override
    public String toString() {
        return "WALLogWriter{" + "logFile=" + logFile + '}';
    }
}
